Hazard Ranking System Glossary of Terms and Acronyms M - Z, Superfund
MCL: Maximum contaminant level.
MCLG: Maximum contaminant level goal.
Maintained Engineered Cover: Vegetated cover, usually made of compacted clean soil. It is generally placed over a source at its closure and is designed and constructed to minimize the migration of liquids through the closed source, function with minimum maintenance, and accommodate settling and subsidence. Maintenance of the integrity and effectiveness of the final cover may include repairing the cap as necessary to correct the effects of settling, subsidence, erosion, and other events.
Major or Designated Water Recreation Area: A major water recreation area is an area used by a large number of people for recreational purposes (e.g., a water theme park). A designated water recreation area is an area designated and maintained by a government body (e.g., local, state, or Federal) as an area for public water recreation (e.g., municipal swimming pool).
Method Detection Limit (MDL): The lowest concentration of a hazardous substance that a method can detect reliably in either a sample or blank.
Multiple-aquifer System: A hydrogeological situation consisting of two or more aquifers that are not interconnected and that underlie sources at the site.
NAAQS: National Ambient Air Quality Standard.
NCP: National Contingency Plan.
NESHAP: National Emission Standard for Hazardous Air Pollutants.
NPDES: National Pollution Discharge Elimination System.
NPL: National Priorities List.
NRC: Nuclear Regulatory Commission
NWI: National Wetlands Inventory
Nearby Individual: Resident or student with the shortest travel distance to any area of observed contamination. If one or more individuals meet the criteria for resident individual, the nearby individual factor value is zero.
Nearby Population: Total number of people who live or attend school within a one-mile travel distance of an area of observed contamination and who do not meet the criteria for resident individual.
Nearest Intake Factor: Factor for evaluating the maximally exposed intake. This factor is based on the presence of actual contamination or, for watersheds where no intake is subject to actual contamination, the flow or depth of the water body at the intake nearest to the probable point of entry within the target distance limit. This factor receives a value from 0 to 50.
Nearest Well Factor: Factor for evaluating the maximally exposed well. This factor is based on the presence of actual contamination or, for aquifers where no target drinking water well is subject to actual contamination, presence of karst and distance to nearest drinking water well. This factor receives one of nine discrete values from 0 to 50.
OSWER: Office of Solid Waste and Emergency Response.
Observed Contamination: Observed contamination is established for the soil exposure pathway only by chemical analysis. The minimum requirements for establishing observed contamination in the soil exposure pathway are (1) analytical data that the concentration of at least one hazardous substance attributable to the site is significantly above background level, (2) information that some portion of that increase is attributable to the site, and (3) the hazardous substance is present at the surface or is covered by two feet or less of cover material (e.g., soil) other than an essentially impenetrable material (e.g., asphalt).
Observed Release: An observed release is established for the ground water, surface water, or air migration pathway either by chemical analysis or by direct observation. The minimum requirements for establishing an observed release by chemical analysis are analytical data demonstrating the presence of a hazardous substance in the medium significantly above background level, and information that some portion of that increase is attributable to the site. The minimum criterion for establishing an observed release by direct observation is evidence that the hazardous substance was placed into or has been seen entering the medium.
Overland Segment: Portion of the hazardous substance migration path from a source to a surface water body.
PA: Preliminary assessment.
PCB: Polychlorinated biphenyls.
PPE: Probable point of entry.
Perennial Water Body: Contains water throughout the year under normal conditions. Under extreme conditions (e.g., severe drought) some water bodies considered perennial may not contain water.
Permeability: The overall ability of water to flow through a geologic material, accounting for all openings in the material (e.g., between grains, through fractures, along lava tubes). For HRS purposes, the terms hydraulic conductivity and permeability are used interchangeably.
Piles (Other): A term reserved for a pile of indeterminate origin that contains hazardous substances.
Population for the Air Migration Pathway: Number of residents, students, and workers regularly present within the target distance limit. This population does not include transient populations such as hotel and restaurant patrons but may include seasonal populations (e.g., a resort area).
Population for the Drinking Water Threat: Number of residents, students, and workers regularly served by surface water intakes that are located within the target distance limit for the surface water bodies evaluated for a given watershed. This population does not includes transients, such as hotel and restaurant patrons, but may include seasonal populations (e.g., a resort area).
Population for the Ground Water Pathway: Number of residents, students (and workers regularly served by wells that are located within the target distance limit for the aquifer being evaluated (and appropriate overlying aquifers). This population does not include transient populations, such as hotel and restaurant patrons, but may include seasonal populations (e.g., a resort area).
Potential Contamination for Listed Sensitive Environments: For listed sensitive environments, potential contamination is established if no portion of the sensitive environment falls within an area that meets the criteria for an observed release and some portion of the sensitive environment is within the target distance limit of a hazardous substance migration path.
Probable Point of Entry (PPE): Point at which the overland segment of a hazardous substance migration path intersects with surface water. A site may have multiple PPEs. The PPE is assigned as the point at which entry of the hazardous substances to surface water is most likely.
Production: Estimate of annual pounds of human food chain organisms harvested for human consumption through all activities, including commercial, recreational, and subsistence fishing. Often times, production can be determined from harvest, catch, or commercial landings data, if the reported data refer only to human food chain organisms.
Productivity: Common surrogate for yield data, often expressed as pounds of human food chain organisms present per acre per year. Productivity data are not equivalent to production estimates and cannot be used for HRS purposes.
Public Recreation Area: Publicly- or privately-owned area used for recreation by individuals not evaluated as workers in the resident population threat.
Pumpage Data: A measure of the volume of water per unit of time discharged from a well, or collected within an intake, either by pumping or free flow. Well pumpage is commonly measured in gallons per minute (gpm), cubic meters per day (m3/day; 1 gpm = 5.45 m3/day), or cubic feet per second (cfs; 1 gpm = 0.0023 cfs). Pumpage data may also be termed well production data, well discharge data, well flow data, well yield data, pumping line data, and for intakes, intake pipe flow data. For HRS purposes, pumpage data relate to the measured or estimated rate of water withdrawal from a well or intake, not from a storage tank or reservoir used as a receptor for water drawn from one or more wells and/or intakes.
QA: Quality assurance.
QC: Quality control.
RCRA: Resource Conservation and Recovery Act.
RI/FS: Remedial investigation/feasibility study.
Recognized Expert: A recognized expert can be a university professor or member of a professional society in a discipline such as ornithology, herpetology, ichthyology, entomology, or botany. The individual also must have published at least one peer-reviewed scientific publication on the area or species of concern.
Recreational Fishing: Fishing for pleasure, amusement, relaxation, or nonsubsistence domestic consumption.
Regular Maintenance: The routine inspection and testing of a well so that it can be ready for immediate use. This is a criterion for determining whether a standby well may be used to evaluate the population factor. Regular maintenance of a standby well may include direct measurement of the static water level, inspection of the well and pump, and testing of the pump. Such activities generally should be conducted at least once per year, and the operating authority should consider the well functional. Rehabilitation activities, with the intent of retaining a standby well in a state of readiness can also be considered regular maintenance. Such activities include pump cleaning and lubrication, screen and gravel pack cleaning, and treatment for incrustation and/or biofouling.
Release Sample: A sample taken to determine whether the concentration of a hazardous substance is significantly above its background level in order to determine whether an observed release (or observed contamination) has occurred.
Resident Individual: A person who lives or attends school or day care on a property with an area of observed contamination and whose residence, school, or day care center, respectively, is on or within 200 feet of the area of observed contamination. HRSGM Section 9.3 provides guidance for identifying resident individuals.
Resident Individual Subject to Level I Concentrations: A resident individual is subject to Level I concentrations if, the concentration of a hazardous substance that meets the criteria for observed contamination is at or above the appropriate benchmark and the sampling location is within the property boundary and within 200 feet of the residence/school. Level I concentrations also may be established if multiple hazardous substances are present below their respective benchmarks, but the I or J index is greater than or equal to one.
Resident Individual Subject to Level II Concentrations: A resident individual not subject to Level I concentrations.
Resident Population: Total number of people meeting the criteria for resident individual.
Resources: Resources considered for the soil exposure pathway are commercial agriculture, commercial silviculture, and commercial livestock production or grazing. Resources must be located on an area of observed contamination. See HRSGM Section 9.6 for additional guidance.
Run-on Control/Runoff Management System, Functioning and Maintained: A functioning and maintained engineered system or structure designed to prevent flow into or onto a source, or, alternatively, to control runoff from a source and prevent hazardous substance migration.
SACM: Superfund Accelerated Cleanup Model.
SARA: Superfund Amendments and Reauthorization Act.
SCDM: Superfund Chemical Data Matrix.
SCS: Soil Conservation Service.
SDWA: Safe Drinking Water Act.
SI: Site inspection.
Salt Water: Water with an average tidal cycle chloride concentration of 18,700 mg/l or greater (corresponding to a salinity greater than 34 parts per thousand).
Sample Quantitation Limit (SQL): The quantity of a substance that can be reasonably quantified given the limits of detection for the methods of analysis and sample characteristics that may affect quantitation (e.g., dilution, concentration).
Scrap Metal or Junk Pile: A pile consisting primarily of scrap metal or discarded durable goods such as appliances, automobiles, auto parts, or batteries, composed of materials that contain or have contained a hazardous substance.
Secondary Containment: As used in HRS Table 3-2, secondary containment is applicable to the evaluation of the containment factor for tanks. Methods of secondary containment include a liner external to the tank, a vault, a double-walled tank, or an equivalent device approved by EPA.
Sensitive Environment in the Air Migration Pathway: A sensitive environment is defined as a wetland (as defined in 40 CFR 230.3) or any area that meets the criteria listed in HRS Table 4-23. No other areas are considered sensitive environments for the air migration pathway.
Sensitive Environment in the Surface Water Pathway: A sensitive environment is defined as a wetland (as defined in 40 CFR 230.3) or any area that meets the criteria listed in HRS Table 4-23. No other areas are considered sensitive environments for the surface water pathway.
Sessile Organisms: Organisms permanently attached or established to some substrate for most of their adult live cycle, such as sponges, barnacles, stalked diatoms, and oysters.
Site: Areas where a hazardous substance has been deposited, stored, disposed, or placed, or has otherwise come to be located. Such areas include multiple sources and may include the area between sources.
Similar Samples: Samples from the same environmental medium that are identical or similar in every way except the degree to which they are impacted by a site. For example, two water samples taken from different points in the same stream would be similar samples if they are identical, except that one is contaminated by runoff from a site, while the other is upstream of the site and unaffected by site runoff.
Single Hydrologic Unit: The combination of geologic materials and aquifers that are determined to be within the same aquifer boundaries, including all interconnected aquifers.
Source: An area where a hazardous substance may have been deposited, stored, disposed, or placed. Also, soil that may have become contaminated as a result of hazardous substance migration. In general, however, the volumes of air, ground water, surface water, and surface water sediments that may have become contaminated through migration are not considered sources.
Source Aggregation: The treatment of two or more areas that could be considered individual sources as one discrete source. The area between two or more individual sources may or may not be considered part of the aggregated source.
Source Hazardous Waste Quantity Factor Value: The highest of the values assigned to a source using the four hazardous waste quantity tiers.
Source Type Other: A source type used when defined source types do not apply. Examples include: contaminated buildings, storm drains, dry wells, injection wells, and French drains. "Other" also can be used for ground water plumes and sediments with no identified source.
Species Habitat: The place where a population of a species normally lives and its surroundings, both living and non-living. Habitat generally is characterized by dominant plant form (e.g., broadleaf deciduous forest) and/or physical characteristics (e.g., fast-moving stream with rocky substrate).
Species Range: The geographic extent over which a species occurs, including areas that comprise suitable habitat as well as those that do not. Current range refers to the geographic extent over which the species occurs at present; historic range refers to the geographic extent over which the species occurred at some time in the past.
Specific Capacity: An alternative term to capacity that is associated with acceptance testing of ground water wells. Specific capacity is reported as the rate at which water is discharged from a well per unit drawdown in the aquifer in which the well is completed. This is usually expressed in gallons per minute per foot (of drawdown) [gpm/ft] or cubic meters per day per meter (of drawdown) [m3/d/m]. The latter term may appear in the technical literature as m2/d.
Standby Intake: A surface water intake held in reserve by a water supply entity (e.g., agency, authority, cooperative, private company, or individual) and maintained for use. It is designated as a drinking water supply to be used during a water supply shortage or emergency such as pump failure, drought, sudden water quality deterioration, or interruption in the regular supply.
Standby Well: A well held in reserve by a water supply entity (e.g., agency, authority, cooperative, private company, or individual) and is maintained for use. It is designated as a drinking water supply well for use during a water shortage or emergency such as pump failure, drought, sudden water quality deterioration, or interruption in the regular supply. Terms commonly used to signify standby wells include standby wells, reserve wells, drought wells, safety wells, emergency wells, backup wells, substitute wells, and uncommitted wells.
Standing Crop: Biomass of all human food chain organisms in a given area of a surface water body at one time. Standing crop data are not equivalent to production estimates and cannot be used for HRS purposes.
Stocking Rate: Number of human food chain organisms (or pounds of human food chain organisms) per unit time introduced into a given surface water body by local, state, or Federal fishery agencies.
Students: A full- or part-time attendee of an educational institution or day care that is served by a well located within the target distance limit.
Subsistence Fishing: Fishing for domestic consumption and nourishment.
Surface Impoundment: A topographic depression, excavation, or diked area, primarily formed from earthen materials (lined or unlined) and designed to hold accumulated liquid wastes, wastes containing free liquids, or sludges that were not backfilled or otherwise covered during periods of deposition; depression may be dry if deposited liquid has evaporated, volatilized or leached, or wet with exposed liquid; structures that may be more specifically described as lagoon, pond, aeration pit, settling pond, tailings pond, sludge pit, etc.; also a surface impoundment that has been covered with soil after the final deposition of waste materials (i.e., buried or backfilled).
Surface Water: Water present at the earth's surface. Surface water includes rivers, lakes, oceans, ocean-like water bodies, and coastal tidal waters, as defined in HRS section 4.0.2.
Surface Water Body: Those surface waters listed in section 4.0.2 and listed on page 8-2.
Surface Water Samples: Samples collected from a water body that can be used to establish an observed release to surface water, including aqueous samples, sediment samples, and tissue samples from essentially sessile benthic organisms. (Tissue samples from non-sessile or non-benthic human food chain organisms (e.g., finfish, lobsters, crabs) may be used to establish Level I fishery contamination but not an observed release.)
TSCA: Toxic Substances Control Act.
TSDF: Treatment, storage, or disposal facility.
Tailings Pile: A pile consisting primarily of any combination of overburden from a mining operation and tailings from a mineral mining, beneficiation, or processing operation.
Tank and Ancillary Equipment: Tanks and associated pipes, pumps, sumps, manifolds, fittings, flanges, and valves used to distribute, meter, or control flow of hazardous substances to or from the tank.
Target Distance Categories: Concentric rings (not necessarily circular) with radii 1/4, 1/2, 1, 2, 3, and 4 miles from the sources at the site. These distance categories are used to group the wells subject to potential contamination for distance weighting.
Target Distance Limit for the Air Migration Pathway: Distance over which population and other targets are evaluated. The target distance limit generally is a four-mile radius from the sources at the site. However, if a sampling point meeting the criteria for an observed release is located beyond the four-mile radius, that point defines the outer boundary of the target distance limit. For example, if an observed release is established six miles from the source, the target distance limit is six miles.
Target Distance Limit for the Ground Water Migration Pathway: The target distance limit is the distance over which targets are evaluated. For the ground water pathway, the target distance limit is generally a four-mile radius from the sources at the site, except: Any drinking water well with an observed release attributed to the site is evaluated, regardless of its distance from the source.
Target Distance Limit (TDL) for the Surface Water Migration Pathway: Distance over which the in-water segment of the hazardous substance migration path is evaluated. The target distance limit extends 15 miles from the PPE in the direction of flow (or radially in lakes, oceans, or coastal tidal waters) or to the most distant sample point establishing an observed release, whichever is greater. In tidally-influenced surface water bodies, an upstream target distance limit is also determined. For some sites (e.g., sites with multiple PPEs), an overall target distance of greater than 15 miles may result.
Target Wells for Aquifer Being Evaluated: Wells that are located within the target distance limits, and completed in the aquifer being evaluated or an overlying aquifer through which hazardous substances would migrate.
Terrestrial Sensitive Environment: A terrestrial sensitive environment is defined as any area that meets the criteria listed in HRS Table 5-5. No other areas are considered terrestrial sensitive environments. Chapter 11 defines each terrestrial sensitive environment and provides sources for identifying terrestrial sensitive environments.
Terrestrial Vertebrate Species: Vertebrate species that lay eggs or bear young outside of water. Included are all reptiles, all birds, most mammals, and those amphibians that lay their eggs in shaded, moist sites on land.
Top of the Aquifer: In unconfined (water table) aquifers, the uppermost elevation of water, accounting for temporal variations, as long as the water table occurs in the materials used as an aquifer. In confined aquifers, the top of the geologic material producing water.
Trash Pile: A pile consisting primarily of paper, garbage, or discarded nondurable goods that contain or have contained a hazardous substance.
Travel Distance: The shortest overland distance an individual would travel from a residence or school to the nearest area of observed contamination, considering natural barriers (e.g., ravines, streams). If there are no natural barriers, the travel distance is the shortest straight-line distance.
Unallocated Source: Not an HRS source type, rather a means of including within the hazardous waste quantity factor those hazardous substances or hazardous wastestreams that are known to be at the site but that cannot be allocated to any specific source. Thus, the term only applies for hazardous waste quantity.
Underground Tank: A tank with its entire surface area below the surface and not visible; however, a fraction of its associated piping may be above the surface.
Vertebrate Species: Animals belonging to the Phylum Chordata, Subphylum Vertebrata. Included are organisms in the Class Agnatha (e.g., lampreys), Class Chrondrichthyes (e.g., sharks, rays), Class Osteichtyhyes (most living forms of fishes), Class Amphibia (e.g., frogs, toads, salamanders), Class Reptilia (e.g., snakes, lizards, turtles, alligators), Class Aves (birds), and Class Mammalia (mammals).
Vertebrate Species with Semi-Aquatic Habits: Vertebrate species that either breed in water but live primarily on land (e.g., many amphibians) or breed out of water but live primarily in water (e.g., waterfowl, turtles, alligators, seals). Species in the former category are termed aquatic species with semi-aquatic habits; species in the latter category are termed terrestrial species with semi-aquatic habits.
WC: Waste characteristics.
Water Withdrawal Rotation Program: Program in which particular surface water intakes within a water supply system are used only for specified intervals, after which other intakes and/or wells are used. Rotation programs are designed to minimize drawdown interference and to maximize efficient use of water in relation to varying water demand. Do not consider an intake that is part of a planned water withdrawal rotation program a standby intake.
Watershed: The region drained by, or contributing water to, a surface water body. Watershed evaluations are performed in two areas:
- Drainage Area: Portion of the watershed upgradient of sources at the site.
- Watershed: Portion of the watershed downgradient of the site. The watershed includes the surface water bodies between the PPEs and the target distance limit (i.e., the in-water segment of the hazardous substance migration path). A single watershed includes all in-water segments that intersect within the target distance limit. A site is in two or more watersheds if two or more hazardous substance migration paths from the sources do not reach a common point within the target distance limit. In these cases, each distinct watershed is evaluated separately.
Well Log: A record of geologic materials with depth based on data obtained beneath a point on the land surface and representative of types, depths, and thicknesses of materials beneath that point. The data may represent visual observations, physical/chemical characterizations, and/or geophysical properties. The record also contains information on wells (drinking and monitoring), where appropriate.
Wellfield Rotation Program: Program in which part of a wellfield is used for a given interval of time and then another part is used. Generally, a pattern is repeated until every supply well has been used, and then the entire cycle is repeated. Rotation programs are used to minimize drawdown interference and to maximize efficient use of water in relation to varying water demand. Do not consider a well that is part of a planned wellfield rotation program a standby well.
Wellhead Protection Area: Areas designated by states according to Section 1428 of the Safe Drinking Water Act, as amended, to protect wells and recharge areas that supply public drinking water systems.
Wetlands: Generally include swamps, marshes, bogs, and similar areas. As defined in 40 CFR 230.3 and the HRS, wetlands are those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Such areas can be natural or constructed. Only areas that meet this definition are eligible to be evaluated as wetlands for HRS purposes. Wetlands identified using other definitions (e.g., the Food Security Act of 1985, the wetlands classification system of the U.S. Fish and Wildlife Service, the 1989 Federal Manual for Identifying and Delineating Jurisdictional Wetlands) are not eligible unless they also meet the 40 CFR 230.3 definition (see HRSGD Section 11.1). Additionally, for HRS purposes, isolated wetlands and wetlands contiguous to rivers, lakes, and coastal tidal waters are defined as surface water bodies.
Worker: A person working on a property with an area of observed contamination and whose workplace area is on or within 200 feet of an area of observed contamination. Both full and part-time workers are considered.
Workplace Area: Any area where workers are regularly present. Areas receiving only brief but regular use (e.g., parking areas, lunch areas) may qualify as work areas if the criteria above are met. The important factor in designating workplace areas is likelihood of exposure rather than duration of exposure.
Yield: Maximum amount of human food chain organisms that could be caught by commercial, recreational, and subsistence fishermen from a given water body. Yield is expressed as weight of human food chain organisms present per unit area (or volume) per unit time. Yield data are not equivalent to production estimates and cannot be used for HRS purposes.